Rude and treat Black Customers differently compared to White Customers

I visited the Shell Rifle Range an hour ago to buy airtime and the teller by the name of Sbusiso was not helpful, rude and even raised his voice at me as I was trying to enquire about recharge airtime. I asked for the manager's numbers and he mentioned that there is no manager at that petrol station. I asked for his number's and his last statement was " to do as I please". This comes to show that black staff do not respect black customers and if I was a white person I would be treated differently and he wouldn't even raise his voice. He even swore at me thinking I didn't hear him when I did saying "voetsek Maan".